Electron tube device for ultra short waves



June 1944- A. ALLERDING 2,351,895

ELECTED TUBE DEVICE FOR ULTRA SHQRT WAVES Filed May 15, 194

' Fig.1

INVENTOR Alfred AI/erd/ng BY ATTORNEZ hereafter called anin'ner conductor. this inner conductor is constructed as a grid Patented June 20, 1944 ELECTRON TUBE DEVICE FOR SHORT WAVES ULTRA 1 Alfred Allerding, Berlin-Frledrichshagen, Germany; vested in the Alien Property Custodian Application May 13, 1941, Serial'No. 393,263 e InGermanyMay 11,1940

2 Claims. (Cl. est-21.5) I

The invention relates to electron tube devices for generating, amplifying or receiving ultra short waves particularly of a wave length of lessthan 1 metre. More specifically the invention relates to tubes comprising a hollow space. con- "structed with metallic surfaces-and serving as a v frequency determining electromagnetic resonator (hollow space resonator);

. .Ultra short wave electron tubes somewhat similar to this type of resonator are described for example in the U. S. A.-Patents 2,128,233 (filingdate March 1, 1935), 2,128,234 (filing date May ,6, 1935) and the applications Serial Number,738,-

. 001 (filing date Augustl, 1934) and Serial Number 171,148 (filing date October26, 1937). will be seen, theinvention relates'to electron tubes in which the surfaces of the hollow space resonator consist of a ceramic material coated T with a good electrical conductor.

U 4 According to the invention a hollow space resonator is used, the volume of the hollow space being limited by the inner surfaces of thewalls of r a hollow body (which may be constructed as a single integral unit or may be formedof several individual parts). A second body having a conductive outer surface is disposed in the inner of the first mentioned hollow body and will be Preferably along one part of its length. One of the novel features of'the invention is that the hollow body consists of ceramic material which is coated on its inner surface with a layer of metal which is suitable for use in high frequency electrical circults, while the inner conductor also being of hollow construction, consists of metal which may be coated with a metallic layer also adapted for high frequency technique.

The ceramic hollow body should be constructed of a material having small dielectric losses. Preferably such materials comprise pure magnesium silicate compounds. The metallic coating of the inner surfaces of the ceramic hollow body are constructed of thin layers 'of a metal which is suited for use in high frequency. elec-' trical" circuits, as for example silver, copper or the like. These layers may be formed of a de posit'by cathode rays.

* A tube constructed according to this invention Comparedhas several important advantages. with. tubes having metallic resonator walls, the

tubes-with ceramic walls are of lighter weight and of smaller dimensions than the first men.-

tioned tubes. In spite of this the ceramic tube is very strong mechanically. The smaller dimensions and the lightnessfinweight are of'spec'ial iinportance,- if a tube i's to 'beused in portable I for instance as in aeroa ultra short wave devices,

planes "or the like. j s

A further'advantagellies inthe fact that it is. possible to sare1y anq-nrm1 support the electrodes at the walls of' the ceramic hollow body.

Thus disturbances whichordinarily follow a buckling ofthe walls 'orsimllar disadvantages caused by the heatradiated by the electrodes can i be largely .avoided and" the presence'of' the so"- called mic'rophonic effect can be absolutely eliminated.

Furthermore a's pecial advantage which is obtainedby employing a device constructed according to this-invention is that the'ceramic parts carrying the electrodes have a very'small coefflcient of expansion. 1 The metal cover of the ceramic body which serves as an electrode and as a resonator surface has as a result of its small thickness the same thermal expansion as the ceramic body itself. Therefore it is certain that with variations of temperature the resonance frequency of the'hollow space, resonator remains practically constant and that after a relatively short time of heatingof the cathode the desired working frequency of the tube can be obtained.

In order to compensate for the-expansion of the metal parts in the ceramic hollow body the supports of these parts may be constructed of an elastic membrane.-

It is a preferred embodiment of this invention that not only are the electrodes formed as a cover for'the ceramic walls and contact thesame with relatively large surfaces but also that the other metallic electrode supports are provided' with large surface areaswhichare in contact with the walls. .Thusan extraordinary large dissipation of heat takes place. This heat. loss results from the conduction of heat of the metallic parts'to'theceramic walls. 'As' will be seen, :I employ the ceramic parts ;to form wholly or at least partly the wall of ajvacuum vessel; ceramic wall howeveris incontact with the outer atmosphere and for this'reason itis maintained 5 at a relatively ,low temperature. I alsdcon-v template the use of a cooling medium which flows through channels formed in the .wall of the res-- onator'or cooling the tube by the use of radiators.

,Further features of the invention' become apparent when-read in the light of the accompany-g ing drawing.

.Asyillustrated in' Fi 1 the electronitub'e com prises a resonator formed as a. concentric Lecherv system, The hollow space resonator is evacuated and is formed of a cylindrical ceramic part 2 which is closed at one end by ceramic plate I while the other end is closed by the cylindrical part 3 which is provided with a glass tube or bulb portion 4. Parts I, 2 and 3 are fused together by glass fusing, enamel fusing, or by a conductive metal such as a semi-conductor, in a. vacuum tight manner. The glass bulb 4 contains the leads 28, 29, 30 for the direct current and is provided with a seal-off tip I! which is constructed in the well known manner. Instead of the glass bulb 4 a ceramic plate may be used to close the cylindrical part 3, means being provided for passing the current leads therethrough.

In the inner portion of the evacuated hollow space resonator a system of electrodes is arranged which consists of a cathode grid and an anode brake field electrode. As is seen in the drawing the anode brake fleld electrode is connected with the outer conductor of the hollow space resonator while the grid forms part of the inner conductor.

According to this invention, the ceramic part 2 serves as a support for the metallic outer conductor and for the anode of the tube. In order to accomplish this dual purpose the ceramic cylinder 2 has a cover of metal on its inner surface, preferably made of silver. This cover (drawn withthick lines) can be made by a cathode ray deposit or in a mechanical manner or may be burned into the ceramic wall. It is preferred to make such cover extraordinarily thin so that it can be led through the seals of the body at 5 to the outside without difficulty, thus serving as the lead-in wires forthe high frequency conductor and the direct current conductor.

The support of the inner conductor of the resonator consists of the grid I and a part 6 having a pipelike construction. A hollow projection 5| is formed in the ceramic plate I adapted to receive the part 6 of the inner conductor (which is made of copper), the part 6 being maintained in positionagainst the wall of the projection 5! by a spring clip 8 in order that violent motion transmitted to the apparatus will not shift the position of the electrodes. Heat generated by the electrodes will be quickly conducted away and dissipated by the thermic contact of part 6 with the wall of the hollow projection 5|. At the other side of the cylindrical part 2 opposite plate I the inner conductor 6 is supported by a corrugated metallic membrane 9 adapted to equalize and compensate for the variations of the length of the inner conductor produced by heat. The membrane 9 is preferably formed like a cap and is pressed against the ofiset 3' of part 3 by the ceramic part [0 and the spring clip II.

The cathode is arranged in the center of the inner conductor 6, I. It may be constructed as a tungsten filament or with special advantage as an indirectly heated oxide coated cathode. When using an oxide coated cathode an additional grid can b arranged between sameand the grid 1.

In Fig. 1 I have shown the end of the cathode system. I: desired the cylindrical part 2 and the flange l2 can be made of one piece.

In the illustrated embodiment the direct current connections are provided at one side and the high frequency current connections are provided at the other side of the tube except for the aerial connection 23. In this embodiment the hollow space resonator to the right is connected to the concentric energy line with outer conductor l1 and inner conductor l8. The outer conductor I1 is preferably galvanically connected to over a certain length especially along a length of A74. Here A is symbolic ofthe wave length of .the oscillations measured in the ceramic material.

The inner conductor l8 of the energy line is connected capacitively to the inner conductor 6, 1 by the conductor l8 which surrounds the projection 5|, the length of which is equivalent to the value ).'/4. In some cases a galvanic contact is also possible and is sometimes advantageous. This contact may be obtained by providing a metallic cover for the continuation 5| which is provided with a radial bore through which the metallic cover is led to the outer atmosphere, the bore being sealed by glazing. Thus a galvanic contact between the conductors 8 and I8 is made.

The conduction of heat is made easier by the through the ceramic wall.

The opposite end of the resonator is short circulted by the capacities formed by'the covers l4 and I5. In this manner the space 20 is discoupled from any high frequency effect, the space containing the direct current leads and other elements. In order to control the discoupling as well as the wave length of the resonator the capacity of the covers l4 and i5 can be made variable. This result may be obtained by employing an insulating ring i6 (preferably made of a ceramic material) adapted to slide in the ceramic part 3 of the tube.

lThe electrode leads extend through the glass wall 4 and are connected to metallic connecting plugs which extend through the walls of a base 2|. If preferred the tube may be closed by a ceramic plate instead of a glass seal and the leadin wires may consist of metallic strips which extend through the ceramic plate. Instead of the commonly used plug pins the socket plate may be v provided with metallic covers having apertures formed therein. I also contemplate employing lead-in wires which may extend through the ceramic wall. With respect to the embodiment shown in Fig. 1, the ceramic tube is bored at 23 and the metal coating is led from the inner surface to the outer surface of the tube. The metal coating may, if desired, encircle the outer side of the ceramic tube 2. The bore 23 is sealed against air leakage by a glass stopper, or other means. The current lead-in wire-connected.

with the metal coating is numbered 3|. In some cases it may be preferred to lead the direct current lead-in wire for the anode through th base.

In order to protect the assembled unit an additional metal tube 22 is being provided which encloses all of the several elements, except for portions of the conductors l1 and I8.

In Fig. 2 an arrangement different from that of Fig. l is shown. In this embodiment the coupling of the outer conductor H with the outer conductor 24 of the resonator takes place in a capacitive manner. To keep radiation losses at a minimum the device is constructed in such manner that the metallic coating 24 is continued at 33 along the seal to the outer surface of the ceramic body 2. Between the metal coating 33 and the conductor i! a ceramic dielectric material is inserted. The coupling condenser is constructed of a length equal to M4. The metal protecting tube 22 similar to that shown in Fig. 1 encloses the outer conductor H for a length equal to one-quarter wave length.

In another very suitable modification the evacuated ceramic body is provided with an inner metal coating forming one part of the resonator. Such a device is shown in Fig. 3. This device is constructed essentially in a manner similar to the resonator shown in Fig. 1. The resonator is constructed having a length equivalent to M4, the electrode system as well as the electron stream being positioned in a potential loop. As is seen in the figure, only one-half of the hollow space is evacuated. A cylindrical steplike ceramic vessel symmetric about its longitu dinal axis .is provided, the inner surface being coated with a metallic element and being airtightly sealed at one end by a ceramic part which Joins a ceramic base plate. The inner conductor I is supported in a manner similar to that shown in Fig. l. A ceramic wall separates the evacuated part 38 from the non-evacuated part 31. Both parts are coupled by the coating l3 which serves as'an anode as well as the metallic part 40 of the outer resonator, these parts forming a capacitance coupling. This coupling, of course,

. may be constructed as shown in Fig. 2. If desired a galvanic coupling may be employed. The energy line l1, I8 is coupled to the resonator in such manner that by extending the outer conductor I! over the wall 39 of resonator part 81 while a capacitance coupling exists between the inner conductor ll of the energy line and the inner conductor 6 of the resonator.

Fig. 4 illustrates how the part 31 of the hollow space resonator may be constructed to eliminate vent the formation of undesired high frequency currents on the outside of the conductor ll.

What I claim is:

1. An electron tube device for generating, amplifying and receiving ultra high frequency electromagnetic oscillations having a length of less than one metre. said device comprising a hollow substantially cylindrical metal tube open at both of its end portions having inner and outer con-v ductor members, said tube having a radially inwardly extending flange portion adapted to engage an outer conductor of a concentric energy line, a substantially cylindrical tube of ceramic material supported at one of its end portions by said outer conductor, the other of said end portions engaging the inner surface of said metal tube, said tube of ceramic material being provided with a radially inwardly extending ring intermediate its ends, said ring having an opening, said tube of ceramic material being provided with a thin metallic coating on the inner surface thereof, and in contact with said metallic tube,

said coating extending over said intermediate ring, a ceramic plate sealingthatend of said ceramic tube engaged by said'outer conductor air tightly, said plate being provided with an outwardly extending hollow projection having mounted on the exterior surface thereof the inner conductor of the said concentric energy line, said wall of said ceramic tube having an opening formed therein,'a metallic ring surrounding said ceramic tube, means fusing said metallic'rin'g and said metallic inner surface lining of said ceramic tube air tightly through said opening'in said wall of said ceramic tube, a current lead-in wire in metallic contact with said metallic ring, a second ceramic tube mounted air tightly within said first ceramic tube and spaced therefrom for a portion of its length, saidsecond ceramic tube being provided with an inwardly radially extending shoulder portion, a metallic diaphragm mounted within said second ceramic tube and tioned within said second ceramic tube, said the formation of unwanted high frequency currents and to avoid energy losses.

As shown in the drawing, the part I1 is formed with a bent over and reversely extending flange portion ll which is held in spaced relation with respect to the line H. The element I1 is formed integrally with the portion 4| and is axially slidable with respect to the longitudinal axis of the element.

The flange portion I is constructed of a length equal to A/4. It is to be noted that an air space is provided intermediate the wall a and the flange ll. Hence, the element" is capacitatively coupled with the wall of the resonator. As will be readily appreciateda resonator constructed accordingtothismodiilcationwlllservetopreopen end being provided with a metallic coating extending for a portion of its length on the exterior and interior sides thereof, resilient means mounted within said second ceramic tube adapted to urge said collar against said diaphragmi a closure member secured to the open end of said second ceramic tube, a base member mounted at one end on said second said ceramic tube, said base member being provided at its other end with contact pins, said contact pins being provided with lead-in wires, said wires extending air tightly through said closure member and said collar member making contact with said cathode.

2. An electron tube device for generating, amplifying and receiving ultra high frequency oscillations of less than one metre as defined by claim 1, and means capacitatively coupling said outer conductor with said metallic coated ceramic tube.

ALFRED ALLERDING. 

